Author: ecpow

My awesome coauthors and I just had a paper come out in Ethology. In this blog post, I’ll break it down for a non-science audience and give some behind-the-scenes info and photos! Here is the full article (open-access) for those interested.

What do reds, oranges, and yellows have in common across the animal kingdom? Danger! Warning! Think of a coral snake or monarch butterfly, advertising their venom or toxicity to potential predators, warning them to stay back, or else! This is known as aposematism, the use of warning colors and patterns. Many animals (like most of the arthropods (insects, arachnids, etc.)) cannot see into the long wavelengths, so how do they know to stay away? First, bold colors are often paired with bold patterns. Coral snakes and monarch caterpillars/butterflies both have orange and yellows paired with black stripes. This achromatic contrast (contrast of brightness, not color) may help predators without color vision to stay away from dangerous prey. Second, aposematic colors are often paired with chemical defenses, so olfactory cues (smell) can help predators with limited vision avoid toxic prey as well.

Oncopeltus fasciatus, the large milkweed bug, is an excellent example of an animal that employs aposematism with both bold bright colors and conspicuous patterns. Milkweed bugs use a long, piercing mouthpart to feed on the inside of the seeds of milkweed, Asclepias. As they feed, they sequester (store) the cardiac glycosides (alkaloids) in the plant to use for their own defense. This is the same mechanism that monarch caterpillars use to defend themselves. Most animals think milkweed is distasteful, but a few insects have evolved to actually harness its toxicity to their own advantage.

(Note: this does not always work, there are lots of predators that are also well-equipped to eat toxic prey. Check out my photo of these predatory stink bugs eating a monarch caterpillar below)

But when predators hunt, how do they know to stay away from dangerous prey? Is aversion (avoidance) of aposematic prey innate (are they born with it)? Or is it learned from experience? Evidence with predators across the animal kingdom suggests that it can be a combination both. Many naive (with no prior experience) predators will avoid red or striped prey. Some will attack once, but quickly learn from the poor taste or aggressive defensive behaviors, that the prey is unsuitable. Further, these aversions (avoidance) of certain prey characteristics (such as red, or stripes, or the shape of a snake) could potentially be changed with experience. Positive experiences with harmless red prey may extinguish (eliminate) a red bias. Vice versa, negative experiences with toxic red prey can reinforce a red bias.

The way a predator knows or learns aversions (predator psychology) is important for biologists like myself to understand the evolution of warning signals in prey. Elaborate color patterns have evolved over millions of years, yet we still do not fully understand their complexity. In addition to warning signals like aposematism, predator psychology research can help us understand the evolution of camouflage or mimicry (when one animal has evolved to look like another, often more dangerous animal to fool predators).

If predators can change their aversions and preferences for prey based on their experience, one might expect that their habitat will be important in driving these experiences. For instance, if the habitat has more toxic red prey, red aversions could be stronger in the predators in that community. Surprisingly, this idea has rarely been tested, only once in birds!

With this experiment, we investigated whether jumping spiders from different populations had different levels of aversion (dislike) for red prey. We did this by bringing the spiders into the laboratory and presenting them with a choice of several termites, painted black or red with enamel paint (Yes, painting termites is as hard and delicate as it sounds!) (photo credit to Lisa Taylor)

Habronattus is a unique genus of jumping spiders (family Salticidae). Habronattus are one of the only genera of all salticids to have long-wavelength vision, meaning they can see reds, oranges, and yellows. They are quite small (4-8mm in length at maturity). To give you an idea of size, here is H. trimaculatus on a US penny (photo credit to Lisa Taylor).

We chose Habronattus brunneus as our jumping spider predator. H. brunneus occurs throughout Florida and on some islands such as the Bahamas. They are sexually dichromatic (males and females are different colors) and quite small in size (spiders were 4-8mm in length in our study).

Habronattus brunneus

Habronattus brunneus

Habronattus brunneus (female (left) and male (right) pictured above, photo credit to Colin Hutton) is a relatively drab species of Habronattus, compared to species like Habronattus americanus, H. pyrrithrix, and H. coecatus that have striking red coloration on their faces. The males of H. brunneus do have green and orange markings on their third pair of legs, that they display to females during courtship (see below, again, credit for these stunning photos to Colin Hutton).

When we found that there were indeed differences between four populations around Florida, my coauthor and undergraduate student at the time, Jeff Coco, conducted habitat surveys. He measured the habitat composition (whether it was covered in leaf litter, grass, sand, etc.) and did thorough sampling for arthropods in the habitat using multiple techniques (sweep netting, leaf-litter sifting, and sticky traps).

One very interesting finding was tens of these little red wasps. These are in the family Trichogrammatidae, but we have NO idea whether they are toxic to spiders! Much of this study (and really all studies) have left us with more questions than answers. Unfortunately, tiny arthropods are often barely taxonomically described, let alone well-studied. These tiny red wasps were most abundant in the populations with less or no red aversion. We know Habronattus will eat other tiny wasps (microhymenoptera), but we do not know if they eat these wasps. If they did, this would more evidence that palatable red prey extinguishes (eliminates) red aversion in jumping spider predators.

At the sites where spiders had higher levels of red aversion, we found more Hemiptera in the families Cicadellidae and Delphacidae, the leaf hoppers and tree hoppers. These insects are often chemically-defended and have striking patterns. While this is just speculative, the higher numbers of these insects at red-averse sites could help to reinforce red biases in the jumping spiders.

Here’s a selection of Cicadellidae from around the world, you can see that they can be quite colorful (photos from Wikimedia Commons)

The oak treehopper, Platycotis vittata (below) and the thorn bug, Umbonia crassicornis are two species that occur in Florida with bright coloration. Studies have shown that lizards reject these bugs as prey after tasting them, which lends evidence to these species being chemically-defended, and advertising this with aposematic coloration and patterning.

In addition to these striking variations in the community of potential prey for our jumping spiders, we also found differences in the habitat composition. Habitat composition (leaf litter, grass, sand, etc) could correlate with species in the habitat, but may also be important for visual systems of the spiders. For instance, more shadows in the environment could reduce the ability to see red. The habitat is dynamic and multi-faceted, even when you’re microscopic!

If you’re still interested, please check out the paper which is packed with a lot more data and information.

And a huge thank you to my wonderful coauthors, this paper wouldn’t exist without the contribution of every one of them!

I was incredibly lucky to have the opportunity to represent the arachnologists gathered in Christchurch in an interview segment on The Project NZ. The Project is a popular nightly news panel here in NZ. Along with Mike Kasumovic from UNSW, I was interviewed by the panel during which I dispelled some common myths around arachnids and attempted to convince the audience that spiders are important biological control agents, an important aspect of a healthy ecosystem, and should be regarded rather than feared. This clip is available in New Zealand but not for overseas viewers.

So here’s a silly screencap instead! I believe the mark that looks like a sharpie pen was actually the editors drawing “webs” and spiders across the screen.

I also interviewed with TV1 whilst out on the mid-week congress excursion and appeared in a short segment.

The Project interview was my first formal appearance on television and it was an awesome experience. Having Mike Kasumovic there as my “co-star” especially helped to lessen the anxiety and make it fun! It felt like a meaningful way to reach many people that might not otherwise interact with spider biologists. Turning fear and disgust into curiosity are important not only to change minds about important, yet less-charismatic taxa (such as spiders), but also for the public to think twice about broader issues facing our natural world.

I’ve been to several conferences now, but never have I been anywhere that I did not have to justify, sell, or explain arachnids as a model system. It was surreal being surrounded by other eight-legged enthusiasts. The community among arachnologists was clearly tightly-knit yet so welcoming. I was impressed at the continuity, with many members making every effort to attend each international meeting, rekindling connections decade after decade and making new ones. I was sold, I certainly intend on making it to the next arachnology meeting! The mid-week excursion took place at Hinewai Reserve on the Banks Peninsula. I was particularly surprised at the amount of Diaea sp. crab spiders I came across. It was a touch dry, but I still managed to find two harvestmen by flipping rocks around the small waterfall and stream during the daytime.

Left: A teeny male Diaea sp. crab spider collected in a sweep net. Right: A Diaea sp. crab spider that I captured mid-molt. It appears that the spider has a “second head” when in fact, it is the shed exoskeleton carapace still attached to the abdomen. You can also see the “dragline” or safety line of silk that the spider hangs from as it completes the delicate molting process.

The drive between Christchurch and Hinewai Reserve was especially scenic.

More conferences! I have been so lucky during my PhD to have the funding and opportunity to build professional relationships and communicate my research via domestic and international meetings. To start off 2019, I attended both the Entomological Society of New Zealand (ESNZ) meeting in Hanmer Springs and the International Congress of Arachnology (ICA) in Christchurch.

At ESNZ, I won 1st prize for best student talk! Here I am with my main supervisor, Greg Holwell.

Morgane and I both rocked our finest entomologically-themed attire. I’ve got a beetle dress, mushroom earrings, and a jumping spider tattoo. Morgane has a dragonfly dress and a sphinx moth necklace.

Group photos! Left is Greg Holwell’s lab group and right is Chrissie Painting’s lab group.

Most of my field work for my personal project has been conducted in Waitomo, New Zealand. I’ve talked about Waitomo before in previous blog posts. It’s an incredible place and I am always thrilled to act as tour guide to introduce visitors (or even kiwis who have never ventured there) to the magic that is karst landscape, glowworm covered walls, diverse harvestmen, and a variety of other endemic invertebrates (such as velvet worms and sheetweb spiders). I took several trips to Waitomo this summer from Dec 2018 to March 2019.

The first two weeks of January, I hosted an Irish undergraduate student who came over for summer research experience, my undergraduate summer student from University of Auckland, and a MSc student working on giraffe weevils at my field site. We added to the sample size of autotomy experiments for one of my data chapters, tried some last ditch efforts to stimulate more natural male-male competition between the harvestmen, and the summer students also got to help with the giraffe weevil project (which included a lot of patience for behavioral observations and the use of a fancy thermal camera).

In February, I also hosted a professional photographer in Waitomo, took a visiting collaborator down for a quick field trip, and guided our new post-doc in the lab around the field site.

Can a sheep farm be any more picturesque?

The closest beach to Waitomo is Marokopa beach. It hosts beautiful, glittery black sand, a rough surf, and seemingly good fishing. The beach is one of my dog’s favorite things about field work, though he is also a huge fan of caves, streams, and forest tracks.

Here’s an assortment of some of the amazing things I’ve photographed in Waitomo this summer!

“Icing sugar” fungus on a sheet-web spider

Female and male Uliodon sp. brown vagrant spiders with prey. The female is eating a centipede (left) while the male is eating some Hemiptera I believe.

Close-up of a glowworm! Not to spoil the magic, but Arachnocampa luminosa is actually the maggot of a fungus gnat, the larvae are predatory and produce bioluminescence (light) and sticky strings of silk to attract and capture prey.

A native bush roach molting, a male tree weta (Hemideina thoracica) molting to adulthood, and a stick insect doing an excellent job of being a stick!

Now for the good stuff! Sure New Zealand scenery is stunning, but we’re clearly here for the bugs.

Here’s a selection of the arthropods we found across our December 2018 Stewart Island/Southland trip.

First up, here’s an assortment of male Pantopsalis phocator. Most NZ harvestmen (well…all NZ harvestmen) have no common name. This one I’ve been affectionately calling “sunset harvestmen” because of the incredible colors that occur. The gradient of silver, orange, red, and yellows reminds me of a sunset or sunrise. These guys were found on Stewart Island as well as on the mainland in the Otago area.

We also found a Forsteropsalis species on Stewart Island, that appears to be Forsteropsalis chiltoni (note that this family of harvestmen is currently under taxonomic revision using molecular sequencing with collaborators). This species is a stunning red color and I was impressed to find this large specimen eating an equally-large freshly-killed crane fly (Tipulidae).

To Morgane’s delight, we also found stick insects on Stewart Island. These were Acanthoxyla sp. Stick insects will sometimes regurgitate to avoid predators. This female almost looks as though she is blowing a bubble of chewing gum. Her food source must make this regurgitation a pink color as most regurgitate brown or green.

Here’s a variety of other arthropods we encountered during the day and night on Stewart Island.

After departing Stewart Island, we remained on the mainland in the very south of the South Island (aptly called ‘Southland’) for a few more days of collecting different harvestmen species. I had previously collected harvestmen in the Catlins Forest and in several sites around Dunedin/Otago 2016 and 2017. We needed to boost our sample sizes for these species, so we returned to these sites again this year. We also collected kelp flies along the beaches in these areas.

There are so many rural beach gems in New Zealand. So much of the country retains its natural beauty that there is seemingly endless farmland and forest along kilometers of cliff side beaches.

Before our flight back to Auckland out of Dunedin, we visited the steepest residential street in the world, Baldwin Street!